Spray devices, such as spray guns, for spraying liquids are commonly used in various industrial applications. To ensure proper operation of the spray device, it is often necessary to monitor the flow generated by the spray device. Presently, there are applications that require rapid detection of the liquid flow generated by a spray device, and in many systems the spray device is required to guarantee that the liquid is actually sprayed when demanded by the system.
In meat and other food processing applications, for example, spray devices are used to surface spray antimicrobials to the product to lower bacterial load or growth. In such spray processes, a specific amount of antimicrobial liquid must be applied based upon the weight of the product and regulatory limits imposed by governmental bodies. This volume typically is dispensed either in a single shot manner or in multiple shots over a specified period of time. If the liquid is not sprayed on the product as programmed, significant product loss or defects can occur. Moreover, many such applications use spray devices that are operated at very high speeds, i.e., they are turned on and off rapidly. The ability to accurately detect the flow in such high speed operation is needed to ensure proper application.
One method of detecting the flow from such spray devices has been the use of light transmitting and receiving sensors, as disclosed in U.S. Pat. No. 7,182,271, assigned to same assignee as the present application, the disclosure of which is incorporated herein by reference. In such sensors, light from a transmitter portion of the sensor is reflected off the spray pattern and provides a signal output from the sensor which can be transmitted to a controller to provide alarming or other calculations using the signal. Such sensors are effective in applications where the environment is “clean”, whereby the sensor is not exposed to falling debris from the application or a dusty or otherwise contaminated environment. The sensors, however, cannot be reliably used in applications in which debris or contaminants can fall onto or otherwise come in contact with the transmitter or receiving portions of the sensor to cause malfunctions.
Other methods of detecting sprayed liquids have undesirably necessitated the insertion of devices into the liquid flow stream, have required complicated calculations based upon the particular liquid, and have not been susceptible to high speed response, such as is necessary for monitoring the flow of spray devices that are operated at rapid on/off cycling in many food processing applications.